Solved All 3CX soft clients connect, all hard phones will not connect.

[Earthbound]

We are on version 18.0 Update 7 (Build 424).

Today all of our hard phones are now unable to register. Some register, then fail cycle through continuously. All the desktop clients are working. The guy that used to be our 3CX guru has moved on a few months ago and this has ended up in my lap. I am a very good network engineer, however 3CX is not in by bailiwick. All of our sip trunks are registered (little green dot next to them). Our license is good for another 2 years. I check our SSL certificate and there is not issue there.

I do not detect any network issues. Nothing about our network has changed recently. No new routers, switches or other such devices. Nobody has complained about internet connectivity so that is not an issue. All of our switches are interconnected with SFP+ at 10G or better.

After the reboot at noon our time today I could see in the event log that all the SIP trunks registered and even a handful of hard phones, but those that do seem to fail within just a minute or so. While connected for that brief minute or so they do function correctly. I was able to used my hard phone to call the receptionist while we were both registered briefly.

Most of our phones are Fanvil X6 or X6U. A couple of Yealink T38b are still around, and our receptionist is on a Yealink T48G.

I am stumped. Can anyone give me a few pointers as to what to investigate.

Thank you!

 

[SweetAction]

I'm a yealink guy, so I'll advise using it to generate a support log so you can see what's happening.
The fact they register and then die is strange - IP Bans, bad creds, etc would not register in the first place - so I need logs first to troubleshoot. But what it sounds like it something is interrupting connection to the 3CX server... maybe a firewall, IDS, etc.

 

[Earthbound]

Thank you for the response! I did manage to discover the issue. It was a DHCP IP conflict, one of our IT staff plugged in a managed router that had a hardcoded IP address. The rookie forgot to test this in the lab before adding it to our network and it wasn't supposed be added until the weekend. Thank you for taking the time to respond, have a great June!